The invention relates to an interchangeable conveying spiral for rock drills for conveying drillings.
Rock drills of the generic type have been known for a long time. In the case of rock drills with a relatively large diameter, the spiral which can be attached onto the drill shank are made as reusable parts which can continue to be used when a blunt drill head is replaced Interchangeable spirals of this type are known, for example, from U.S. Pat. No. 3,372,763, German Offenlegungsschrift No. 30,44,775 or German Offenlegungsschrift No. 25,43,578.
A known interchangeable spiral consists, for example, of a continuous support tube on which the spiral-shaped transporting shoulder is mounted by welding or brazing. The interchangeable spiral consisting of a jacket tube and transporting shoulder can also be made as a cast, solid part with appropriate remachining. In another form of an interchangeable spiral, the jacket tube is dispensed with, so that only the transporting shoulder surrounds the drill shank in a spiral shape, with intermediate spaces remaining between the individual spiral pitches.
The known embodiments of interchangeable spirals have the disadvantage that they can be manufactured in complex manner as a solid part having a jacket tube and transporting shoulder and are therefore expensive. The interchangeable spiral without a jacket tube can close in on itself during the rotational motion when increased resistance occurs in the frictional area of the wall.